1. Field of the Invention
The present invention relates to air assist fuel injectors, and, more particularly, to a sealing arrangement for air assist fuel injectors having an interface cap.
2. Description of the Related Art
Conventional fuel injectors are configured to deliver a quantity of fuel to a combustion cylinder of an engine. To increase combustion efficiency and decrease pollutants, it is desirable to atomize the delivered fuel. Generally speaking, atomization of fuel can be achieved by supplying high pressure fuel to conventional fuel injectors, or atomizing low pressure fuel with pressurized gas, i.e., "air assist fuel injection."
Conventional air assist fuel injectors are typically mounted to a rail, which houses a conventional fuel injector and also defines a mount for the air assist fuel injector. The conventional fuel injector and the rail are configured such that a metered quantity of fuel is delivered from the fuel injector to the air assist fuel injector. Additionally, the rail includes a number of passageways that deliver pressurized air to the air assist fuel injector. The air assist fuel injector atomizes the low pressure fuel with the pressurized air and conveys the air and fuel mixture to the combustion chamber of an engine.
The pressurized air from the rail and the metered quantity of fuel from the conventional fuel injector typically enter the conventional air assist fuel injector through an inlet in the center of an armature. Thereafter, the fuel and air travel through the interior of a poppet, and exit the poppet through slots near the head of the poppet. The poppet is attached to the armature, which is actuated by energizing a solenoid. When the solenoid is energized, the armature will overcome the force of a spring and move toward a leg. Because the poppet is attached to the armature, the head of the poppet will lift off a seat so that a metered quantity of atomized fuel is delivered to the combustion chamber of an engine.
Because liquid fuel and air travel through conventional air assist fuel injectors, it is desirable to seal the solenoid of such air assist fuel injectors from the conveyed liquid fuel and air. It is also desirable to seal the interface between each air assist fuel injector and the rail to prevent liquid fuel and air from leaking to an area outside the air assist fuel injector, such as to an engine compartment of a vehicle. The solenoid of most conventional air assist fuel injectors is sealed from the liquid fuel and gas by multiple o-rings located in the solenoid of the air assist fuel injector. Unfortunately, this configuration increases the size of the air assist fuel injector, which is problematic given the strict space constraints of many internal combustion engine applications.
Other conventional air assists fuel injectors do not incorporate multiple o-rings within the solenoid, but instead provide an o-ring between a flange of a sleeve and the rail to define an axial seal. This configuration attempts to seal the solenoid from the liquid fuel and gas and also attempts to seal the interface between the air assist fuel injector and the rail. However, this axial seal configuration is prone to leak when subject to vibration, such as that associated with some internal combustion applications. Furthermore, this conventional seal configuration is also not suitable for air assist fuel injectors that utilize an interface cap for the liquid fuel and air.